光暗环境对活性污泥法处理性能的影响

Effect of light and dark environment on performance of activated sludge process

由于加盖式、地下式污水处理厂的活性污泥处于黑暗环境,通过对比光、暗环境的碳氮磷去除性能,并从溶解性有机物、动力学参数、胞外聚合物EPS、粒径、菌落结构分析了活性污泥处理污水的光敏性。结果表明,光环境出水更优,光、暗环境的出水COD分别为15 mg/L、20 mg/L,氨氮质量浓度分别为0. 67 mg/L、0. 88 mg/L,正磷酸盐质量浓度分别为0. 40 mg/L、0. 63 mg/L。暗环境下,聚磷菌减少而聚糖菌增多,污泥的聚β羟基丁酸和EPS中的磷酸基团减少,导致出水磷升高;污泥对有机物的亲和力下降,出水腐殖度高;污泥的生长和衰减变慢,内源呼吸比例升高,粒径变大,污泥结构更稳定,沉降性能更好。暗环境下聚磷菌Dechloromonas减少,聚糖菌Defluviicoccus和Propionivibrio增多,反硝化菌减少,硝化菌增多。

The given paper aims at making an evaluation of sun-light effect on the activated sludge treatment of domestic sewage,with comparison of COD,ammonia,orthophosphate removal between the sunlight and dark environment. What is more,analysis of the mechanism is made in terms of the dissolved organic matters,the kinetic parameters,extracellular polymeric substances,particle size and the bacterial community. The results indicate that the activated sludge under the sunlight condition behaves better than those in the dark condition. In detail,in the light and dark conditions,the effluent COD is 14. 6 mg/L,20. 2 mg/L,with the ammonia nitrogen being 0. 67 mg/L,0. 88 mg/L,and the orthophosphate being 0. 40 mg/L,0. 63 mg/L, respectively.The effluent under the light and dark condition proves statistically different. When synthetic sewage concentration ranges at low,medium,and high,performance in the dark is also inferior to that in the light. In the dark condition,the storage of poly-3-hydroxybutyrate(PHB) of sludge and phosphorus-groups in extracellular polymeric substances(EPS) tends to decrease,Polyphosphate accumulating organisms(PAOs) decrease while the glucose accumulating organisms(GAOs) tend to increase,all of the above result in the lower phosphorus removal. Besides,the UV spectra absorption and the UV characteristic parameters indicate that the effluent COD contains more macromolecular organics and rich in humic substances,which could be degraded by the sunlight. Much more ammonia is released from the organic nitrogen compounds in the anaerobic phase. Furthermore,the growth and decay of activated sludge get slower due to the declined affinity to the substrate,confirmed by the specific oxygen uptaking rate,the maximum rate vmaxand the half-saturation coefficient KS,while the ratio of endogenous respiration is promoted. The particle size of activated sludge becomes bigger to promote the structure of the activated sludge more stable. As to the bacterial community,denitrifying bacteria including Thauera,OD1, Persicirhabdus and Mizugakiibacter decreased, Dechloromonas responsible for P removal decrease,GAOs of Defluviicoccus and Propionivibrio increase, Plasticicumulans, Nitrospirillum,Nitrosomonas, Nitrospira, and the unclassified bacterial genera increase. Therefore,it is necessary to monitor competition between PAOs and GAOs,and adopt coagulation or membrane filtration to reduce bacterial metabolites in underground wastewater treatment.